Telephone system



Aug. 15, 1933. A. FLAD TELEPHONE SYSTEM Filed Jan. 7, 1932 BL; I

-Inuen or"- HHEF Flacl .Flfg

rain 'ir Ass. 15,3933.

' Application'Ja'nuary 'z, 1932, Serial No. 585,254," Y "and'in Germany February 21,1931

teams; (01. 179-16)- The invention relates toja'circuit arrangement for the initiationof switching operations in telephone'fsystems.

The problem forming the basis for. the invention consists in carrying out switching operations by influencing a relay, connected up to the telephone lines, by means of alternating or direct current while preventing the unwanted additional currents such as condenser discharges from causing interruptions in the operation of the relay without using special symmetry equalizing devices. This is achieved by a relay, connected up in series with a glow lamp or neon tube, carrying out the required switching operation when influenced by a sufliciently strong current sent out over one of the leads of the telephone line.

The device according to the invention is usedwith particular advantage in systems in which initiation of switching operations are to be carried out over lines subject to the influence of high tension. The glow lamp being so constructed that it flashes over and lights up only when a current of sufiicient strength passes 5 through it thus causing the relay to be energized, the arrangement oifers special security against the relay being unintentionally influenced by the additional currents which due to various courses are generated in lines carrying heavy current and which may have harmful effects on the operaton ver the telephone lines.

' Furthermore, even though the relay which is to be actuated, when using the device according to the invention, is connected direct to the leads of the telephone line, the connection includes the high resistance in the glow lamp so that the symmetry of the lines is not disturbed and special symmetry equalizing devices need not be provided. In prior circuit arrangements 40 for controlling a relay over one trunk conductor,

one of two alternatives had to be employed,

either the relay was not permanently connected to the trunk conductor,.in which case a preliminary signal had to be sent to connect it up, or the relay was permanently connected to one trunk conductor, in which case additional apparatus had to be connected to the other trunk conductor in order to secure a balance.

A further advantage of the device is that other signals may be transmitted over the lead to which the relay is connected without such signals being interrupted, thereby, provided these signals are transmitted by applying a tension to the lead in question lower than that required to light the lamp.

in the accompanying drawing;

Fig. 1 shows a telephone line F1 over which a connection may be set up in any known manner, either by the intervention of an operator or 0 automatically over switches, between the subscribers Tnl and Tn2 associated with the two exchanges A and B. A direct current relay R1 connected to the battery Btl is located at one end of the line and connected to the b-lead of 5 this line over a glow lamp G1. At the other end of the line earth may be applied to this lead over contact kl. The voltage of the battery Btl is such that the current passing in the circuit which, when set up on the closing of contact k1, extends over the b-lead and the glow lamp causes the glow lamp to light up, which in turn causes the relay to be energized. If a definite switching operation is to be initiated over the line, such as, for example, the release of the existing connection, the'circuit for battery Btl is closed by contact k1 so that the relay R1 may be energized, which then carries out the required switching operation.

In Fig. 2 is shown. an arrangement which difiers from that shown in Fig. 1 by alternating current being used instead of direct current.

The arrangement according to Fig. 3 is characterized in that the direct current from the battery B13 is superimposed by the alternating current supplied by the alternating source of supply W3, the direct current in such a case being so chosen that the voltage derived from the alternating and the direct tension causes the glow lamp G3 to be lighted with a subsequent connecting up of relay R3.

What is claimed is:

1. In a telephone system, a trunk line including two conductors, a glow lamp, a relay connected to one of said conductors at one end of the trunk line in series with said lamp, a source of high potential alternating current, and means for connecting said current source to said one conductor at the other end of the trunk line to cause said lamp to flash over and operate said rela 2. In a telephone system, a trunk line including two conductors, a glow lamp, a source of direct current, a relay connected to one of said conductors at one end of the trunk line in series with said lamp, 9. source of alternating current, and means for connecting said second current source to said one conductor at the other end'of the trunk line to cause said lamp to flash over whereby a circuit is completed for operat- Three embodiments of the invention are shown ing said. relay from current from said first current; source.

3. In a telephone system, a trunk line, a glow lamp, a relay permanently connected to the near end of the trunk line in series with said lamp, a source of high potential current, and means for connecting said current source to the distant end of the trunk line to cause said lamp to flash over and operate said-relay. f y p 4. In a telephone system, a trunk line, :a glow lamp, a relay and a source of low potential current permanently connected in series to the near end of the trunk line, a source of high potential current, and means for connecting said 'last current source to the distant end of the trunk line to flash over said lamp and thereby permitssaid relay to operate from current -from-said first current source.

5. In a telephone system, a-lineincluding two talking conductors, means for qestablishng-m talking circuit between two station s over the two conductors of the line in series; acontrol relay permanently connected between one of said "conductors'an'd ground at one end of the line, a normally open gl'ow lamp connected in series withsaid relay and said one conductor and in inserting a glow lamp in the permament connection between the relay and said one conductor so that the superimposed circuit is normallyopen.

'7. The method of superimposing a grounded circuit on a' metallicloop circuit without unbalancing the-jsame-which consists in permanently connecting arelay between ground and one conductor of the-lpop oircuit, in inserting a glow lampbetween-the relay and said one conductor to maintain the superimposed circuit normally open, and in providing means for applying a high potential current to said one conductor to cause said lamp 'toflash over; 

